Method for producing annular forgings

ABSTRACT

In the process of free forging an ingot made of titanium alloy with an Alpha + Beta structure is subjected to multiple plastic deformation in its axial, radial, and tangential directions with an overall degree of deformation in each of these directions being not less than 60 percent of the total deformation, and with sucessive changing of the direction of the deforming force. On completion of deformation annealing is performed at a temperature somewhat below the temperature of phase transformation of the alloy from Beta to Alpha + Beta structure.

United States Patent [191 Grekov et a1.

[4 1 Feb. 18, 1975 METHOD FOR PRODUCING ANNULAR FORGINGS [76] Inventors: Nikolai Alexandrovich Grekov,

Tikhoretsky prospekt, 9, korpus 7, kv. 83; Galina lvanovna Arkovenko, prospekt Metallistov, 113, kv. 49; Elena Petrovna Silina, ulitsa Shatelena, 8, kv. 66; Natalia Petrovna Shifrina, Varshavskaya ulitsa, 22, kv. 4, all of Leningrad; Tamara Nikolaevna Sazonova, Srednaya Pervomaiskaya ulitsa, 19, kv. 13; Vasily Yakovlevich Kleimenov, Srednaya Pervomaiskaya ulitsa, 12, kv. 10, both of Moscow; Josif Sholomovich Kvater, ulitsa Krasnykh partizan, 3, kv. 5; Moisei Grigorievich Zlatkin, ulitsa Yakovu Severdlova, 34, kv. 22; Valdislav Alexandrovich Mirmelshtein, ulitsa Pushkinskaya, 14, kv. 15; Alexei lvanovich Potapov, prospekt Crdzhonikidze, 24, kv. 1, Sverdlovsk all of U.S.S.R

Filed: May 21, 1973 Appl. No.: 362,345

Related U.S. Application Data [63] Continuation of Ser. No. 92,525, Nov. 24, 1970,

abandoned.

[52] U.S. Cl 148/115 R, 75/175.5, 148/127, 148/11.5 F

51]RZT3TITIT 021d [58] Field of Search 148/115 F, 12.7,133, 148/131, 130;75/175.5, 11.5 R

[56] References Cited UNITED STATES PATENTS 2,968,586 1/1961 Yordahl 148/127 X 3,313,138 4/1967 Spring et a1. F 3,481,799 12/1969 Day et a1 F 3,489,617 1/1970 Wuerfel 148/115 F OTHER PUBLICATIONS Young, J. F.; Materials and Processes; New York, 1954, pp. 748-750 and 765.

Primary Examiner-Walter R. Satterfield Attorney, Agent, or Firm Holman & Stern [5 7] ABSTRACT 4 Claims, No Drawings METHOD FOR PRODUCING ANNULAR FORGINGS This is a continuation, of application Ser. No. 92,525, filed Nov. 24, 1970, and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to methods of making annular forgings intended to act under high mechanical loads, and can be used in the production of annular forgings for shroud rings of the rotors of powerful turbogenerators rated at 500 MW and more.

Known in the art is a method to make blanks for the rotor shroud rings by free forging, wherein the ingot is drawn, upset, pierced through, and expanded, the blank being then heat treated and strain-hardened.

Steel shroud rings made by this method, although possessing adequate mechanical properties in normal conditions of operation, may cause failure of turbogenerators under high mechanical loads in conditions of elevated temperature and increased moisture, thus requiring frequent examinations and replacement of the rings.

The well-known advantages of titanium alloys their high strength and corrosion resistance result in the development of these alloys in aircraft construction and other industries for producing heavy-duty components featuring high resistance to corrosion and elevated temperatures.

Known in the prior art are methods of producing blanks of components weighing up to 300 kg by free forging or swaging the ingots of titanium alloys with a single-phase or double-phase (a B) structure. Known for such components are conditions of hot plastic deformation and heat treatment, that provide for high strength and plasticity of titanium alloy forgings. In particular, for titanium alloys with a double -phase a B structure hot plastic deformation is advised with these components being heated to temperatures corresponding to the a B structure. Also known are more precise parameters of thermomechanical treatment of titanium alloys with an a B double-phase structure, namely working of the ingot at temperatures 4090C below the temperature point of transformation of B structure of the alloy into a B structure, and to a degree of deformation equaling 4070 percent.

The prior art conditions of hot plastic deformation in.

the production of titanium alloy articles do not secure uniform and equiaxial structure throughout the cross section of blanks of large size and weight, i.e. 500 kg and more, for example, of forgings of rotor shroud rings for powerful turbogenerators.

SUMMARY OF THE INVENTION The object of the present invention is to choose such conditions of the working method to produce annular forgings by hot plastic deformation of an ingot of titanium-based alloys with a double-phase a B structure with the amount ofB phase being up to 30 percent; that will ensure the obtaining of a uniform and equiaxial structure throughout the cross section of the article.

The above and other objects are achieved according to the invention by multiple plastic deformation of the ingot in the axial, radial, and tangential directions with an overall degree of deformation in each of these directions being not less than 60 percent of the total deformation, and with successive changing of the direction of the deforming force, the deformation in the last forging operation being not less than 40 percent. Also, the blank heating temperature is successively reduced from a temperature which exceeds by 5 O-80C the temperature point of the phase transformation of the alloy from B to a B structure at the first forging operation, to a temperature 20-30C below said temperature point at the last forging operation, and on completion of plastic deformation the blank is annealed at temperatures below said temperature point.

The indicated solution provides for the action of forces of varying directions on all the layers of the forging in the most plastic condition of the ingot, working thereof being finished in the temperature zone of a B state of the alloy structure, which makes it possible to obtain a uniform and equiaxial structure throughout the cross section of the forging.

To avoid cracks, the first of the forging operations preferably includes deforming the ingot in the radial direction.

In accordance with one of its embodiments the invention may provide for the following conditions and succession of plastic deformation realized in forging operations: ingot drawing with a lateral deformation of 3050 percent at a temperature which exceeds by 50-80C the temperature point of phase transformation of the alloy from B to a B structure; upsetting with a deformation of 50-70 percent and hole piercing at a temperature exceeding by 3050C said temperature point; drawing the hollow blank with a deformation of 30-40 percent, expansion with deformation of 20-30 percent, and upsetting with deformation of 10-30 percent at a temperature: which is 20 30C higher than said temperature point; after these operations the blank is drawn with a relative deformation of up to 30 percent, and expanded to deformation of 40-50 percent, at temperatures 20-30C below the said temperature point.

Advantageously, annealing of the obtained forgings should be performed in the following succession: heating the forging to 800-900C and keeping it at this temperature for not less than one hour, with subsequent complete air cooling, then second heating to a temperature of 550650C with maintenance at this temperature for not less than 1 hour, and with subsequent complete cooling.

DETAILED DESCRIPTION OF THE INVENTION Described below are exemplary embodiments of the method for producing an annular forging for the turbogenerator rotor shroud from a titanium-based alloy with a content of Al being 6%, Mo 2.5%, Cr 2%, and with the temperature of phase transformation from B into a B structure being 980C.

EXAMPLE I An ingot weighing 1300 kg is heated to a temperature of 1050C and drawn under free forging to a deformation of 38% in its cross section. Next the thus obtained blank is heated to a temperature of 1000C and upset to an axial deformation of 62 percent of the total deformation, and then pierced through. After the hollow blank is heated to l000C, it is placed on a mandrel and drawn with a deformation of 36 percent in the ring depth. The blank is again heated. to l000C and expanded on a mandrel to a deformation of 26 percent in wall thickness. After heating to l000C the blank is upset with, deformation of 29 percent in depth. Next, at a temperature of 1000C the blank is drawn on a mandrel with deformation in the depth amounting to 25 percent. Then at a temperature of 950C the blank is ing by 50-80C the temperature of phase transformation from B to a B structure; subjecting said ingot to successive multiple plastic deformations in the axial, radial, and tangential directions of the ingot with an cXpnnded to the required dimensions of the forging the 5 overall degree of deformation being not less than 60 degree of deformation in walliniokness being 42 P percent to form a blank; decreasing each heating step o g during said deformation from said first heating tempert eomptetton of the forgmg opetattons t fotgmg ature to a temperature 2030C below the temperat e to mom temperature; Anneatttlg of the ture of said phase transformation before the last mentorgmg e performed as follows: heatmg to 9 Ct e 10 tioned deformation, the temperature of each heating ing at th1s temperature for one hour, and an coolmg. Step being between and losoec; and annealing the EXAMPLE 2 blank on completion of said plastic deformation, the annealin bein erformed atatemperature somewhat The mmat mgot a lvelght 0f.2600 kg'ls heated below s aid t iiiperature of phase transformation t a temperature of 1040 thls tempetatute the whereby a large annular blank having solely a uniform ingot 1s upset by 52 percent 1n depth, and 1s pierced l restructure is reduced through. After that the hollow blank is heated to mic p I IOZOOC and l d d L M thi t r t r e method as in claim 1, whereln the first of the p ace i a man re em-pe a u e for in o erat1ons com rises deformm them ot 1n the drawing is accomplished to a deformatlon in depth p g g reaching 39 percent. After this operation and heating radial dlrecnon to 1000C the blank is expanded with a deformation of 1 mettmd as "i Ctalm t 17 percent in the ring thickness mation is realizeddurmg the forging operat ons in the Next the bank is heated to 980C with subsequent follow ng succession and under the following condiupsetting to a deformation of 30 percent in depth. lIlOIlSI lngot drawlng withalateral deformation amount- After this operation the blank is heated to 950C, at mg to 3040 percent of the overeat] dftotmatton at a which temperature it is drawn with deformation of temperature wh'eh exceeds by 50 C the tempera percent in depth. Final expansion is accomplished after tute of phase 'ttanstotmfttton of the alloy from B to a heating to 950C, the deformation in the ring thickness 5 Structure? upsetttttg wtth a deformation of 50-79 being 40 percent. After finishing the said operations cent and hole Piercing at a temperature exceeding by the blank is air-cooled and heat treated in the follo- 30 Said Phase transformation temperature; wiong Succession; drawing the hollow blank to a deformation of 30-40 The forging is heated to 870C, held at this temperapercent, expanding with deformation of 2030 P t. ture for 1 hour, and air-cooled. Then it is heated to a and upsetting with deformation o 0- pe n at a temperature of 650C, and maintained at this temperamp r r being 03 C highe than said phase ture for 2 hours with subsequent air cooling, transformation temperature; then drawing the blank The mechanical properties f f i d d with a relative deformation of up to 30 percent and exunder the described conditions of the process, as obpanding with deformation of -50 percent at a temtained on specimens cut out tangentially at 20C, are as perature from 2030C below said phase transformafollows: tion temperature.

example wall tensile yield elongation relative impact thickness strength point 8% reduction ductilmm kg/mm kg/mm ity kg/cm What is claimed is: 4. The method as in claim 3, wherein annealing is l. A method for producing large annular forgings of carried out by heating the blank to 800-900C and more than about 500 kg. by freely forging an ingot keeping it at this temperature for not less than 1 hour, made of titanium-based alloys with a double-phase a with subsequent complete air cooling; then secondary B structure, the amount of B phase being up to 30 perheating to a temperature of 550-650C and maintaincent, which comprises the steps of heating the ingot being at this temperature for not less than 1 hour; and f1- fore successive forging steps, the first heating exceednally completely cooling. 

1. A METHOD FOR PRODUCING LARGE ANNULAR FORGINGS OF MORE THAN ABOUT 500KG. BY FREELY FORGING AN INGOT MADE OF TITANIUM-BASED ALLOYS WISTH A DOUBLE-PHASE A+B STRUCTURE, THE AMOUNT OF B PHASE BEING UP TO 30 PERCENT, WHICH COMPRISES THE STEPS OF HEATING THE INGOT BEFORE SUCCESSIVE FORGING STEPS, THE FIRST HEATING EXCEEDING BY 50*-80*C THE TEMPERATURE OF PHASE TRANSFORMATION FROM B TO A + B STRUCTURE; SUBJECTING SAID INGOT TO SUCCESSIVE MULTIPLE PLASTIC DEFORMATIONS IN THE AXIAL, RADIAL, AND TANGENTIAL DIRECTIONS OF THE INGOT WITH AN OVERALL DEGREE OF DEFORMATION BEING NOT LESS THAN 60 PERCENT TO FORM A BLANK; DECREASING EACH HEATING STEP DURING SAID DEFORMATION FROM SAID FIRST HEATING TEMPERATURE TO A TEMPERATURE 20*-30*C BELOW THE TEMPERATURE OF SAID PHASE TRANSFORMATION BEFORE THE LAST MENTIONED DEFORMATION, THE TEMPERATURE OF EACH HEATING STEP BEING BETWEEN 950* AND1050*C; AND ANNEALING THE BLANK ON COMPLETION OF SAID PLASTIC DEFORMATION, THE ANNEALING BEING PERFORMED AT A TEMPERATURE SOMEWHAT BELOW SAID TEMPERATURE OF PHASE TRANSFORMATION WHEREBY AT LARGE ANNULAR BLANK HAVING SOLELY A UNIFORM EQUIAXIAL MICROSTRUCTURE IS PRODUCED.
 2. The method as in claim 1, wherein the first of the forging operations comprises deforming the ingot in the radial direction.
 3. The method as in claim 1, wherein plastic deformation is realized during the forging operations in the following succession and under the following conditions: ingot drawing with a lateral deformation amounting to 30-50 percent of the overall deformation at a temperature which exceeds by 50*-80*C the temperature of phase transformation of the alloy from Beta to Alpha + Beta structure; upsetting with a deformation of 50-70 percent and hole piercing at a temperature exceeding by 30*-50*C said phase transformation temperature; drawing the hollow blank to a deformation of 30-40 percent, expanding with deformation of 20-30 percent, and upsetting with deformation of 10-30 percent at a temperature being 20*-30*C higher than said phase transformation temperature; then drawing the blank with a relative deformation of up to 30 percent and expanding with deformation of 40-50 percent at a temperature from 20*-30*C below said phase transformation temperature.
 4. The method as in claim 3, wherein annealing is carried out by heating the blank to 800*-900*C and keeping it at this temperature for not less than 1 hour, with subsequent complete air cooling; then secondary heating to a temperature of 550*-650*C and maintaining at this temperature for not less than 1 hour; and finally completely cooling. 